Traffic signal controller



July l5, 1941. V, w, LEONARD 2,249,481

TRAFFIC S IGNAL CO NTROLLER Filed Oct. 3, 1939 2 Sheets-Sheet l A Figi.

Vincent VV. Leonard,

Att Orr# ey.

July 15, 1941. v. w. LEONARD 2,249,481

TRAFFIC SIGNAL CONTROLLER Inventor: Vin cent VV. Leon ard.,

H is Attorney.

Patented July 15, 1941 TRAFFIC SIGNAL CONTROLLER Vincent W. Leonard, Saugus, Mass., assigner to General Electric Company, a corporation of New York Application October 3, 1939, Serial No. 297,703

5 Claims.

My invention relates to trailic signal controllers, and more particularly to an improved apparatus for indicating the failure of a signal lamp.

One object of my invention is to provide an indicating means which is automatically energized when a signal lamp becomes inoperative.

Another object of my invention is to provide a lamp failure or outage indicating means which will become effective upon the failure of any one of several signaling lamps and will become ineilective as soon as such lamp is replaced by an operative lamp.

For a better understanding of my invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

In the accompanying drawings, Fig. 1 illustrates, diagrammatically. one type of trailic signal controller provided with a lamp failure indicating means built in accordance with my invention; Fig. 2 is a diagrammatic illustration of the same controller provided with a modification of my invention; and Fig. 3 is a chart indicating one schedule of signal operations.

Referring to the drawings in detail, Fig. 1 discloses a traflic signal controller comprising essentially a driving motor I Il, a timing dial driven by the motor, and a rotary switch preferably in the form of a drum controller I2 which operates suitable'contacts connected into the circuits of groups of traffic signals N, S. E, and W. The drum controller I2 is operated by a suitable mechanism controlled by the dial through contacts actuated by keys mounted in the dial and through circuits connecting said contacts to said mechanism. y

The motor I is preferably a self-starting synchronous motor of the type disclosedin U. S. Patent No. 1,430,867 Warren. It is diagrammatically illustrated as having a eld I3, an armature enclosed in a casing I4, and a shaft I5 driven by the armature through a speed reducing gearing which is enclosed lin an enlarged casing I6 attached to and made a part of the casing |4. The motor drives the timing dial through a pair of pinions Il, l1' and a shaft l5. The shaft I also carries the actuating wheel 84' for a signal ashing mechanism.

'I'he timing dial comprises a disc Il mounted directly on the shaft l5 and driven thereby in the direction indicated by the arrow. The disc is provided with equally spaced radial slots i9, near its periphery, arranged to receive keys 20 and 2|; there being, in the present instance, ve keys 20 and one key 2|, the key 2| being longer than key 20 and being provided with a notch 2|'.

Adjacent to dial is a resilient contact arm 4| xed at its one end on a suitable support (not shown) and at its free end provided with a contact 22 and a block 42. The contact 22 is attached to the upper side of the contact arm and the block 42 is attached to the lower side of this arm and has a beveled lower endwhich projects into the path of movement of and is adapted to be engaged by the keys 20. When a key 20 moves under block 42 during rotation of dial Il', it momentarily raises the free end of arm 4| to bring the contact 22 into engagement with a xed con-v tact 22'.

Also, adjacent to dial is a second resilient crm 40 fixed at its outer end on a suitable support (not shown). At its free end it is provided with a contact 23 and a block 45 having a beveled lower end which projects into theV path oi', and is adapted to be engaged by, the key 2|. When key 2| is moved under block 45 during rotation of dial it momentarily raises the free end of arm 40 to bring the contact 23 into engagement with a ixed contact 23'. The notch 2|' in key 2| is in line with block 42; therefore, when key 2| is in position' to operate block 45, the block 42 passes through this notch 2|' and is not lifted to close the contacts 22-22'.` 4

'I'he drum controller I2 comprises a series of seven cams 30 mounted on shaft 29 which are adapted to operate contacts mounted adjacent to the cam surfaces respectively. The cam surfaces are so arranged that when the cams are rotated in a step-by-step manner through a xed number of positions in each revolution, by a suitable operating mechanism, the contacts are' moved to open or close circuits with cooperating contacts in accordance with a predetermined schedule. In the present instance the cams are successively moved to six positions, in each revolution, which comprises one cycle of signal operations. The first cam on the left-hand end of the drum operates a contact 31, and the other cams each operate a contact and thereby respectively control circuits of the several signal lamps.

The mechanism for advancing the drum comprises an electromagnetically operated ratchet mechanism including a magnet coil 25 provided with an armature 26. 'I'he armature is connected to the free end of an arm 21 which is pivoted at its other end on the shaft 29 and carries a pawl 21'. The free end of the pawl cooperates with a ratchet wheel 28 which is rigidly attached to the end of the shaf-t 29. This pawl slides over the surface of the ratchet wheel when the coil 25 ls energized to lift its armature. When the coil 25 is deenergized, the amature drops and moves the pawl counterclockwise. During this movement, the free end of the pawl engages a tooth face on the ratchet wheel, and thereby moves the ratchet wheel with it. The length of this movement is proportioned to move the drum to its next position. In the present instance the movement of the pawl and the teeth on the ratchet wheel are arranged to rotate the wheel through one revolution in six operations. The drum cams are correspondingly arranged for sixpcsition operation.

The manner of timing the movement of the drum I2 and the manner in which it is maintained in a definite relationship with the continuously rotating dial, may be understood from a consideration of the circuits interconnecting the dial operated contacts and the magnet of the advancing mechanism. The electric current needed for this operation is received through a conductor 32 indicated on the left-hand side of the drawing. The motor I is started by the closure of a switch 33 which closes a circuit between the conductor 32 and one end of the motor iieid winding I3. The other end of this eld winding is connected to a grounded terminal 44. The motor then rotates the dial Il, causing keys 20 to intermittently close a circuit by raising the contact 22. This circuit may be traced from the conductor 32 through the magnet coil 25 of the drum advance mechanism, conductor 34, a switch 35, conductor 35, contacts 31-31, conductor`38, contacts 2222, arm 4l, conductor 43, to the grounded terminal 44. At each closure of this circuit, the drum mechanism advances the drum to a succeeding position. The time interval between movements of the drum is proportional to the spacing of the keys in the slots of the dial as long as a uniform speed is maintained by the motor.

It may be pointed out that since both dial and drum are rotated by separate mechanisms, there is a possibility of starting them off in any desired relationship which would obtain as long as the drum is advanced at each closure of the circuit through contacts 22-22'. 'I'he spacing between the keys 20 is not uniform, however, and it is therefore necessary, for proper operation, to maintain a definite relationship between the drum and the dial so that each position of the drum is maintained for the desired time period. For this purpose the drum is caused to open -the circuit of the drum-advance coil in one of its six positions. This is eected by the contacts 31 and 31'. When the contacts 31-31' are separated, the circuit to the magnet coil 25 through contacts 22-22' is opened, and keys 2l are unable to effect an advancement of the drum. For

the purpose of advancing the drum beyond this position a shunt circuit is established by the closure of contacts 22-22' eected by the key 2| at the instant that the dail is in the proper relation to the drum.

The key 2l is preferably placed in the dial in a position which marks the end of the time interval allotted to the main street right of way. The contacts 31-31 are opened when the drum is moved to its main street right-of-way DOsition and remain open in this position of the drum. When the dial reaches its proper position in relation to the drum, the key 2| closes the circuit by raising contact 23. The established circuit may be traced from conductor 32 through the coil 25, conductor 34, switch 35, conductor 35',

. contact arm 40, contacts 23-23', conductor,

interconnected contacts 48, conductor 43, contacts SII-5I of a relay 52, conductors 53, 54, 55, switch 56, conductor 51, to grounded terminal 44. That instant at which the dial II reaches the position at which it closes contacts 23-23' marks the end of the time interval for the drum position in which contacts 31-31' are separated. At the succeeding position of the drum, contacts 31-31' are closed and keys 20 again effect an advancement of the drum. The relationship of the drum and dial is therefore checked at each revolution, the drum being held stationary until the dial moves to the proper position relatively to the drum.

The drum may also b advanced by a manual manipulation of the switch 35. The switch is provided with a cooperating grounded contact 35'. When the switch arm engages this contact a circuit is established through the coil 25. By intermittently moving the switch to engage this contact, the drum I2 may be advanced at will, the circuits through the dial-operated contacts being simultaneously inoperative since they are opened at the contact 35.-

Further details of this controller may be found by reference to copending application Serial No. 203,888, led April 23, 1938, by R. A. Reid, and assigned to the assignee of the present application.

The trailic signal groups are designated as N, S, E, and W, are energized through circuits controlled by the above described mechanism. They are placed at the four corners of a street intersection to regulate trame moving in four directions along. two intersectlng streets, the directions chosen for purpose of illustration being the four cardinal points of the compass. Each of the groups is provided with a red, amber, and green lamp designated respectively by the letters R, A, and G. The signals for each street are connected in pairs since trailic moving in opposite directions in one street is signalled simultaneously; i. e., the N-S signals are connected in pairs and the E-W signals are connected in pairs.

In Fig. 1, my invention is applied to indicate the failure of the red lamp in each signal group, although my invention may be applied also to indicate the failure or outage of the green lamp in each group. Briefly, the mechanism for producing such indication includes an electro-magnetic switch or relay connected into the circuit of each red lamp. This switch remains in one position as long as the respective red lamp circuit carries current during the signal period, and moves to a second position when the current is interrupted during such signal period. When this switch moves to its second position, it energizes an electromagnetic relay which in turn interrupts the circuits to all the signal lamps and establishes a new circuit for an indicating device. In the present instance, the amber lamps of all the groups are energized simultaneously through a flashing device for the purpose of indicating the failure of the red lamp.

The signal lamps are all energized from the common source conductor 32 and the respective circuits are completed through the drum operated contact 4I which are connected to the ground terminal 44. For the purpose of describing my invention, the circuits for the amber and red lamps only are necessary. 'I'he conductors 2,249,481 leading from the proper drum controller contacts to the green lamps are not shown, so that the red and amber lamp circuits may be more readily traced. 'I'hese conductors are merely continuous conductors of sulcient capacity to carry the current of the green lamps and are indicated in Fig. 2. Two cams and cooperating contacts are provided, one for the E-W green lamps, and one for.the N-'S green lamps.

The amber lamp circuits for the two intersecting highways may be traced from the source conductor l32 to the respective drum operated contacts in two groups; i, e. N and S and E. W. The circuits for the N, S amber lamps may be traced from conductor 32 through the amber lamp in the S group to a conductor 60, and from conductor 32 through the amber lamp in the N group to a conductor 6| which also joins the conductor 60. The common circuit for these two amber lamps continues through the conductor 60 to a movable contact 63 on a relay 52, astationary contact 62 of the relay,` conductor 64, to a contact 65 of the drum controller. In predetermined positions of the drum, the cam 30 aligned with this contact 65 and with a cooperating contact 48, will effect an engagement of the two contacts and thereby close a circuit which may be traced to grounded terminal 44 through conductor 49, relay contacts 50-5I, conductors 53, 54, 55, switch 56, conductor 51, and ground terminal 44. The circuit for the E and W amber lamps may be traced from conductor 32 through the amber lamp in the E group, to a conductor 66, and from conductor 32 through the amber lamp in the W group to a conductor 61 which is in turn connected to the conductor 66. The common circuit for these two amber lamps continues through the conductor 66, through movable contact 69 and'stationary contact 68 of the relay 52, through a conductor 10 to a contact 1| on the drum controller. Here again, a circuit is closed during predetermined positions of the drum by a cam 30, which is in line with the contact 1| and a cooperating contact 48, and the circuit continues to grounded terminal 44.

It may be here noted that relay 52 controls the circuits of the amber lamps through two pairs of contacts 63-62 and (iS-68, and controls the circuit for all the lamps through the third pair of contacts 50-5l which are in the common grounded return conductor of the lamp circuits. pairs of contacts are in engaged relation and the circuits therethrough have been traced. For actuating the movable contacts the relay is provided with a coil 12 which when energized raises the movable contacts 63, 50, and 69 to break the circuits therethrough and to establish a new common circuit for the four amber lamps. To establish this new common circuit, the contacts 63 and 89, which are terminals respectively for the NS and E-W amber lamps, respectively are raised to engage stationary contacts 13 and 14 which are connected to a single conductor 15. When so raised, these contacts establish the new circuit, through the amber lamps, which continues through conductor 15, a lter choke coil 16, a conductor 18 to a stationary contact 19, a movable contact 80, a contact arm 8|, conductor 55, switch 56, conductor 51 to grounded terminal 44. The contact arm 8| which supports the contact 80 is pivotally mounted on a stationary block 82 and the free end thereof is provided with a nose 83 which rides on the star wheel 84 mount- In the position illustrated, the three ed on the motor shaft l5.. I'he circuit for the amber lamps is thereby intermittently closed and opened at contacts 19-80 to effect a dashing of al1 the amber lamps. The lter choke coil 16 cooperates with a condenser 11 connected between conductor 54 and conductor 15 for the purpose of suppressing the high frequency magnetic waves emanating from the arc at the contacts 19 and 80, thereby preventing interference with radio reception in the Vicinity of the controller.

The relay 52 which eiects the circuits of all the signal lamps is operated in response to the outage of any one of the red lamps. This operation is obtained by providing a switch in each red (R) lamp circuit which operates to energize the operating coil 12 of the relay 52 when a red lamp burns out. Referring to Fig. 1, the switches in the red lamp circuits are illustrated as electromagnetic relays 90, 9|, 92 and 93. The relay is connected into the circuit of the red lamp in the W group of signals, the relay 9| is in the circuit of the red lamp in the E group; relay 92 is in the red lamp circuit of the N group, and relay 93 is in the red lamp circuit of the S group of signals.

Relay 90, the first of the above-mentioned relays, is provided with anarmature 94 controlled by a series coil 95 connected in series with the W-red lamp and by a coil 96 connected in shunt to the same lamp. This latter coil may be called, for the sake of convenience, a potential coil. The

circuit for the W-red lamp may be traced from the positive conductor 32 through the lamp to a conductor 91, series coil 95, conductor 98, to a movable contact 99 on the relay. The relay is shown in its deenergized position, vand in this position, contact 99 is in engagement with a stationary contact |00. The circuit for the lamp continues through conductors |0| and |02 to a contact |03 on the rotary drum switch |2. A cam 30 on this drum moves the contact |03 into engagement with a contact 40 at predetermined positions of the drum to complete the circuit to the grounded terminal 44 48, conductor 49, contacts 50-5I, conductors 53, 54, 55, switch 56 and conductor 51, as already traced for the amber lamps. The circuit for coil 96 may be traced from conductor 32 to conductors |04 and |05 through the coil 96 and from the coil through conductor 98, relay contacts 99, |00, conductors |0| and |02 to drum contact |03. During the signal period for this lamp the circuit continues through contacts 40 to grounded terminal 44 as traced for the lamp circuit. As long as current flows to the lamp, the two coils 35 and 96 are both energized and act, upon the armature 94, in opposite directions; the potential coil tending to lift the armature and the series coil tending to hold it in its normal position. The power of the coils is such that no movement of the armature takes place. When the series coil becomes deenergized, however, during a signal period when the potential coil is normally energized, the potential coil raises the relay contacts and elects an operation of the amber lamp relay 52. Y

vThe operation of relay 90 breaks the normal red lamp circuit and establishes two circuits, one of these two being a locking circuit for the potential coil;'and the other a circuit for'the operating coil 12 of the amber lamp relay. The circuit to the operating coil 12 of the amber lamp relay 52 may be traced from the positive conductor 32 to conductors |04, |05, and movable through the contact l gages a stationary contact |01 and the circuit 'contact |00 on the-relay 90. When the relay armature is raised, the movable contactf|06 en- W-red lamp through the conductor |02 by the rotating drum switch |2. The relay elements and contacts correspond to the elements of the relay 90,'and are accordingly worked, -a single accent mark being used to distinguish them from the elements of the relay 90. The coils 95' and 95' are energized simultaneously with the coils of relay 90. The contacts |01 and are also connected to conductors and 53, respectively, so that in response-to an outage of the E-red lamp, the relay 52 is operated as in vresponse to an outage of the W-red lamp.

tionary contacts |00 and are so arranged,

that the moving contact 99 does not leave contact |00 before it engages it maintains a continuous energization of the coil 95 during the change of connections. The circuit through the coil is then maintained, independently of the drum contacts, through the conductor 53 to which the contact is connected, and through conductors 54, 55, switch 56, conductor 51 to the grounded terminal 44.

The operation ofthe amber relay effects an interruption of the normal operation o f the signals and or the drum switch I2. The 'separation of the relay contacts 50- 5| effects both of these conditions. The signal circuits are interrupted -instantly upon the separation of the contacts l5| because these contacts break the common return circuit for all the lamps. The drum switch is advanced by the actuationof switch 22-22' by the keys 20, until the drum reaches the .position at which the interlock contacts 31-31', in this operating circuit, are opened and the keys become ineiIective. The key 2li cannot advance the drum, through the circuit of contacts 23-232 because the return circuit for these contacts operated by 2|, is also broken` at the contacts IO-ll. v Y

When it is desired to renew the burned out lamp, the controller is placed into operation for one cycle to ena-ble an operator to detect the inoperative lamp and place a new one in its socket. A push button switch ||0, in the operating circuit of the amber lamp relay, is provided for this purpose. As long as this switch is held in its circuit interrupting position, the circuit ior coil 12 is broken and the relay 52 will drop its contacts. The controller will then operate the signals normally. When the broken lamp In this manner The elements of the relays 92 and 93 correspond to the elements of the relays 90 and 9|. They are marked with double and triple accent marks to distinguish them from the same elements oi the other relays.

The series relays 92 and 93 are connected at one end to the N-red and S-red lamps respectively through conductors ||3 and ||4. The common circuit for the series coils of these relays is closed by the drum switch |2 through contacts 40| I5 and a conductor I5.

The circuit closed by these relays in response to 1 an outage of either lamp N-red or S-red is that for coil 12-and is the same as for relays 90 and 9|.

The controller may be shifted to ilashing amber operation by a hand operated switch ||1. This fswitch ||1 energizes the amber lamp relay coil has been detected, this switch is allowed to close.

Il, conductor 51 to ground terminal 44. The

series coil 95 of the relay 90 will then be energized and the relay contacts. will be moved to their lower position, the series coil being made powerful enough to overcome the pull of the potential coil. The amber lamp relay coil circuit is thereby opened at the contacts |05|01 of this relay. The relay 52 will, accordingly, drop to its first position and the controller will continue its normal sequence operation.

The same operation occurs when any one of the other three red lamps becomes inoperative. The relays in the red lamp circuits are exactly alike and are arranged to operate relay 52 in the same manner. The E-red lamp is connected in series with the relay 9| through conductor ||2. This lamp is energized simultaneously with the 12 by closing a circuit 'from the positive conductor 32 through a conductor ||0, and through the coli to ground through the normally closed push button switch H0. A time controlled switch indicated diagrammatically by a coil ||9 and a pair of contacts |20 may also be used to initiate hashing amber light operation by closing the circuit between conductor |04 and |00. The coil 12 is then energized through a circuit from conductor 32 through conductors |04, |00, coil 12, conductor |09, switch ||0, to ground.

In Fig. 2, I have illustrated a modification of my invention. In this figure, the invention is applied tothe same tratlic signal controllerthat is illustrated in Fig. 1, corresponding elements being designated by the same numerals. The relay 52, Whlchis the relay used in Fig. 1 to operate .the outage indication, is in this modification controlled by an arrangement of one relay, connected in series with the red lamps during their respective operating periods, and an auxiliary relay. This arrangement is more economical in that lessl relays are used than in the arrangement of Fig. 1.

Referring to this ilgure in detail, the controller includes the motor l0, dial and controller I2, as in Fig. 1. The signals are arranged in two groups E-W and N-S having red (R), amber (A) and green (G) lamps respectively. They are permanently connected to the feed conductor 32 and are respectively connected to contacts on the drum controller by individual conductors.v

'I'he relay 52 is provided, as in the arrangement of Fig. 1, to change the circuits of the lamps for flashing amber operation. The operating coil 12 thereof is controlled. however, by a series relay ductor |33, normally closed time-clock contacts |34, conductor |35, switch |36, conductors |31, |33'and 55, switch 56, conductors 51 and 43' to ground terminal 44. A circuit of this same relay coilmay also be traced through the E-W'red lamp. This latter circuit continues from the positive conductor 32 through the E-W red lamp to conductor |40, controller contacts |4||'42 to conductor |3| and to the relay coil |21. 'I'he remainder of the circuit from the relay coil to ground is the same as forfthe N-S red lamp. 'I'he series coil is, therefore, energized during the red lamp period for N-S and also during the red lamp period for the E-W signal groups, and consequently, is continuously energized during the normal operation of the red lamps. This relay |25 is provided with a single moving contact |43 which is raised when the relay coil is energized and which drops to engage stationary contacts |44|45 when the relay coil is deenergized.

'Ihe intermediate relay |26 is provided sov as to prevent the application of an electric impulse to the amber lamp relay, throughthe contacts of the series relay, when power is rst applied to the control apparatus. The contacts of the intermediate relay are closed whenever any one of the red lamps is energized and are open when the lamps are deenergized. The contacts of the series relay are open when the red lamps are energized, and are closed when the red lamps are deenergized, The contacts of these two relays are, placed in series, in the operating coil circuit of the amber lamp relay, so that when the intermediate relay is energized and the series relay becomes deenergized, the amber lamp relay circuit is closed and the controller operation is changed to flashing amber. When the signals are turned off, the intermediate relay opens its contacts and the series relay closes its contacts. Therefore, when the current is turned on, the circuit to the relay coil 12 remains open.

The intermediate relay |26 is provided with `a coil |46 which is energized through a pair of contacts |41|48 on the signal operating drum I2, a cam IBI being arranged to hold these contacts in closed or open position in accordance with a predetermined chart of operations. An example of such a chart is illustrated in Fig. 3 and will be explained in connection with the operation of this controller.

The circuit for the intermediate-relay coil |46 may be traced from lthe source conductor 32 through conductors |50, |5I, |52 to the coil |46, conductor |53, controller contacts |41|43 conductor |54, normally closed push button switch |55, conductor |33, time switch contacts |34, conductor |35, switch |36, conductors |31, |33, 55, switch 56, conductors 51, 43' to grounded terminal 44.

This relay |26 is providedwith a pair of movable contacts |56-I56' and a pair of stationaryv contacts |51I58. When the coil |46 is energized the contacts of the relay establish a locking circuit and partly establish a circuit that is completed only when the contacts of the series relay are closed. The amber relay coil circuit may be traced from conductor 32 through conductors |50, |5l, |52' to relay coil 12 and .through conductors |59 and |60 to contacts |56-|'51. The contact |51 is connected to the stationary contact |45 of the series relay by a conductor |51'. When the series relay is closed, the circuit continues from contact |45 through bridging contact |43, contact |44 to conductor |54. 'I'he circuit then continues through conductor |54' switch |55, to conductor |33 and time switchcontacts |34 to grounded terminal 44 as previously' traced for the intermediate relay coil circuit.

At the time that the intermediate relay establishes the amber relay circuit, it also establishes a locking circuit for its own coil |46. This circuit is established by the closure of contacts I'56'| 58. The moving contact |56' is connected to con# ductor |53 to which. one endof the coil |46 is also connected. When the relay operates, the' lamp relay is energized as soon as the series relay drops, due to a lack of current in its coil, and the intermediate relay establishes a circuit for itself through its own contacts and thereby becomes independent of the drum contacts I41-I48. The intermediate relay contacts are placed in series with the series relay contacts so as to prevent an operation of the amber lamp at times when switching operations4 other than the normal signal sequence operations are performed. Thus, for instance when current is rst turned on, the series relay is deenergized and has closed the circuit to the amber lamp relay. The intermediate relay is also deenergized and its contacts are open and the amber lamp relay coil remains deenergized.

If it were not for the intermediate relay, which is also deenergized at this time, the amber relay would snap into hashing amber position before the series relay had an opportunity to open its contacts in this amber relay coil circuit. This same condition holds when, under the influence of the time-switch contacts |34, the controller is set to operate on sequence operation. The contacts of the time switch operate with a snapaction so that the normal sequence operation circuits are established before thel amber relay drops into deenergized' position or, alternately, before the series relay breaks the circuit to the amber relay coil. In either case, the amber lamp relay would remain closed if the intermediate relay did not prevent this operation by interposing a break in the amber relay coil circuit.

When a red lamp burns out, the series relay drops to close its contacts and, the intermediate relay being closed, establishes the circuit to the amber relay 52 as above traced. When a new lamp is substituted for the burned out lamp, the circuit to the new lamp is not automatically reestablished in this modication, because the cir.. cuit for the coil |21 of the relay |25 is broken by the center contacts 50-5l of the relay 52. In the circuit of Fig. 1, a, bypass circuit is established under these circumstances by the relay contacts and 99. The series coil is thereby automatically reenergized when a new lamp is placed in the socket of the burned out lamp, and

.the relay 52 is thereby deenergized to establish establish normal connections, and thereby establishes a circuit for the series coil I2'I through the replaced lamp, This circuit may be traced from positive conductor I2 through either of the red lamps and its controller contacts to conductor.

I2I, through coil |21, conductor |321 contacts l-IL conductor |33, contacts I, conductor |35, switch |38, conductors lil-|38, 55, switch 5|, conductors I1 and to ground contact M.

In Fig. 3 I have illustrated a chart of operations for the controller above described. The chart indicates that the controller I2 has six positions or periods, numbered vertically 1 to 6. There are eight cams on the controller drum. The first cam (left to right) operates the drumlock contacts )1 -31'. The closed position of the contacts is indicated by crosses in the rectangular spaces of the chart. Reading the chart, under this interlock cam it is indicated that the contacts are open in the third period. 'I'he six rows indicate the closed and open positions for the red, green, and amber signals` respectively.

'I'he last cam marked I 6I operates the contacts Ill-|48 which are in the intermediate relay coil circuit. This cam is divided into twelve positions so that the operation of the contacts Ill- |48 may be offset in relation to the operation of the red lamp contacts. It is indicated in this chart that in periods 4 and 6 both red lamps are out.

In order that the amber relay circuit may not be operated under these circumstances, the intermediate relay contacts are opened by the cam ISI during the movement of the drum from period 3 to 4. The cam surface is, therefore, so arranged that the contacts Ill-I are opened one-half step before the red lamp contacts are opened. The contacts remain open during the fourth period and are closed during the fifth period. It is indicated, however, that the contacts are closed during the first of the two half periods into whichthis cam is divided. 'Ihis simply means that while the drum is in its fifth position the contacts are closed. When the drum is being moved toits sixth position, the cam permits the contacts to open when it has traveled only one half the distance to this next position.

The speciiic signal operating cycle illustrated by the chart, Fig. 3, is the most commonly used 4-period cycle. 'I'his consists of two right-ofway positions for each of two intersecting highways, and a caution period between each change. It is often desired, however, to use additional periods, such as, for example, periods during which certain turns are permitted, or periods during which pedestrain trame is permitted exclusively. To provide for such contingencies, the drum I2 is provided with a 6-position star wheel 28 requiring six operations for a complete revolution of the drum. The timing dial II is correspondingly provided with five keys 2l, and one key 2 I, by means of which the coil 25 is energized six times during each revolution of the dial. The cams 30 onA the drum I2 are, however, arranged painted green. is chosen to move the drum at this time, or conversely, the drum lock contacts $1- 31 are opened in this position of the drum, for the reason that if a delay should occur due to the non-synchronism of the drum with the dial, it is preferable to hold the drum in the position in which it delays the least amount of trailic. This position is, therefore, that position in which the right-of-way is indicated to the more importantof the two intersecting streets.

Referring to the dials illustrated in Figs. 1 and 2, it may be stated that the two keys 2|! pr the green key 2| (in the direction of rotatiom' are the keys which effect a movement of the drum from position I through position 2 to position l. These two keys are painted black to distinguish them from the signal changing keys. 'Ihe key 2l, following key 2l, effects an operation of the drum from position I to position I. The second key following key 2I and illustrated as closing the contacts 22, effects a movement of thel drum from position 5 to position l. The sixth key is the key immediately below the key which is in the act of closing the contacts 22. This key effects a movement of the drum from position l to position I, and marks the beginning of what is preferably termed the mainv streetgreen period, that is, the period in which the more important of two intersecting streets is given the right of way. The actual spacing of the keys in the slots of the dial I I is arranged separately for each intersection, and in the illustrated example, no speciflc timing is intended to be shown.

What I claim as new and desire to secure by Letters Patent of the United States, is:

l. In a traic signal system, the combination of a group of trafiic signals, a motor operated for the i-period cycle, and in order to provide for,

the discrepancies between the number of positions on the drum and the number of periods in the cycle, one period of the cycle is spread over three positions of the drum.

Referring to the chart again, it will be noted that the green lamp. for the E-W street and the red lamp for the N--S street are energized in each of positions I, 2, and 3. It will also be noted that the drum interlock contacts are opened in position 3. The drum cannot be moved there fore, from position 3 to position I by a key 2li, as has explained above. Key 2 I, which is preferably switch operable to energize said signals in a predetermined sequence and at predetermined time intervals, a relay responsive to current flowing to said signals `and arranged to operate its contacts to closed position upon the failure of one of said signals, a second relay operated to closed contact position only when current is available for operating said signals, signal failure indicating means, and a third relay energized through the contacts of said first two relays upon the failure of said signal, said third relay operating to interrupt said sequence operation of said group of signals and to energize said failure indicating means.

2. In a traiilc signal system the combination of a group of electrically operated traffic signals, a motor operated switch operable to energize said signals ina predetermined sequence and at predetermined time intervals, a relay in the eircuit of said signals and operated to close its contacts when current is available for energizing said signals, a second relay energizedto open its contacts only when current is available for a predetermined one of said signals, and'a third relay energized through the said first two relays upon the failure of said one signal during its signaling period, said third relay interrupting said sequence operation and energizing a predetermined other one of said signals to indicate the failure of said first mentioned signal. i

'3. In a trame signal system the combination of a group of traflic signals, a motor operated switch operable to energize said signals in a predetermined sequence and at predetermined time intervals, a relay in the circuit of said lamps and operated to closed contact position when current is available for operating said signals, a second relay energized and operated to open contact position only when current is connected to one of said signals, and a third relay energized through the contacts of said iirst two relays upon the failure of said one signal during its signaling period, a second circuit for another of said signals, as. ashing mechanism in said circuit, said third relay interrupting said sequence operation and energizing said predetermined other one of said signals through said second circuit for obtaining a ashing operation of said last mentioned signal dicating means, and a third relay energized through the closed contacts of saidrst two relays to operate said failure indicating means.

5. In a tralc signal system the combination of a group of traiiic signals, a switch operable to energize said signals in a predetermined sequence at .predetermined time intervals. a relay responsive to current available for operating said signals, a second relay operated by current owing in one of said signals to one position and operable to a secondposition upon failure of said signal, failure indicating means, energized in response to a failure of said signal through said iirst two relays, said last relay being operated to interrupt said sequence operation and to energize said failure indicating means, and means for operating said last relay to restore normal sequence operation in response to a resumption of current ow in said failed signal circuit.

VINCENT W. LEONARD.

a third relay 

